Relative to vehicles that use internal combustion engines as the sole power source, emerging vehicle designs take advantage of the relative efficiency of electric motors, particularly at low speeds, as an alternate power source. For example, a hybrid electric vehicle combines the selective operation of an electric motor to enhance fuel economy, such as by selectively shutting off the engine when the vehicle is at a standstill, via regenerative braking, or via electric propulsion, depending on the vehicle configuration. Other designs such as the plug-in hybrid electric vehicle and extended range electric vehicle provide off-board and on-board energy recharging capabilities, respectively. Relative to conventional vehicles, these emerging designs may provide superior fuel economy under certain driving profiles.